Obesity is a preventable condition that contributes significantly to morbidity and mortality. A women's risk for obesity, as well as cardiovascular disease and osteoporosis, increases dramatically with menopause due to normal and lifestyle changes. Furthermore, many perimenopausal women are already at risk for obesity based upon current overweight or obesity, former obesity, or a family history of obesity. In light of much evidence that reversal of obesity generally is difficult and unsuccessful long-term, a preventive approach that emphasizes modest lifestyle modifications may be superior in promoting long-term behavioral changes and weight control with advancing age. Therefore, the primary aim of this study is to assess the effectiveness of a modest lifestyle intervention program or preventing gains in body weight, whole body bat mass, and abdominal adipose tissue during a 2-year period in perimenopausal and early postmenopausal women who are at risk for obesity. A second aim is to determine the effects of the intervention on daily physical activity, which will be calculated from total daily expenditure and resting metabolic rate, as determined by the doubly labeled water method and indirect calorimetry, respectively. A randomized, controlled trial will be used to evaluate the intervention in female employees of a large Midwestern medical center. The intervention is a modest lifestyle modification program that will focus on teaching participants ways to modify their dietary habits and incorporate additional physical activity, as a means of altering daily energy balance to prevent weight gain during the 2-year intervention period. The 4 components of the intervention include: 1) reducing dietary fat intake; 2) increasing daily physical activity; 3) two consecutive days per month of low-fat, low-calorie meals prepared either in the metabolic kitchen of the General Clinical Research Center or by the participant; and 4) a "study- buddy" system, in which each participant is paired with a buddy with whom she is to keep in the frequent contact, discuss goals and progress, and motive. The results of this project are intended to provide valuable information regarding lifestyle programs that may assist women in controlling body weight at a time when weight gain is common.